ORIGINAL: opjose
LiPo's ( with a regulator ) are robust and problem free and pose no big point of failure.
I have seen people use these, and have seen good, expensive regulators fail - ending their day of flying. And by adding the weight of a regulator, you're re-gaining any weight you may have lost by using LiPos.
I just see this as turning something simple into something complicated, and adding one more thing that can go wrong.